Overflow cell for plating strip



Nov. 21, 1967 T. CARTER OVBRFLOW CELL FOR PLATING STRlP Filed Jan. 24, 1964 I INVENTOR DAN/EL 7T GARTER Attorney United States Patent.

ABSTRACT OF THE DISCLOSURE An overflow plating cell for traveling strip is provided with an inlet for circulating electrolyte, which extends the full width of the tray along which the-strip travels for contact with the electrolyte. This reduces the turbulence and splashing as the-electrolyte enters the trough. A pump for circulating the electrolyte has its outlet connected to the cell inlet.

This invention relates to an electroplating cell for coating metal strip and, in particular, to a cell having provie sions for circulating electrolyte therethrough and for conducting strip therealong immersed in the electrolyte at a slight depth below the liquid surface.

Surface-type electrolytic cells for plating strip are known generally. Those with which I am familiar require guide rolls for keeping the metal strip in contact with the electrolyte and liquid seals for confining the latter in its container. I have invented a novel cell which obviates these limitations yet insures constant contact between the strip and a supply of fresh electrolyte, and prevents the latter from being carried away from the area of contact.

In a preferred embodiment of the invention, I provide an elongated tray, the bottom of which serves as anode, having a weir at one end and an entry chamber or inlet at the other. A pump supplies electrolyte from a tank to the inlet for flow along the tray toward the weir. A collecting trough below the weir returns the overflow to the tank. Metal strip to be plated is conducted over the length of the tray at a level such that it is immersed to a slight depth in the electrolyte flowing through the tray. The inlet or entry chamber flares from a small dimension on the pump-delivery side to a width substantially equal to that of the tray at the point of connection therewith.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the present preferred embodiment. In the drawings:

FIGURE 1 is a partial plan view of the inlet chamber and the connections thereto;

FIGURE 2 is a view in vertical longitudinal section, somewhat diagrammatic, showing my improved cell with parts in elevation; and

FIGURES 3 and 4 are transverse sections taken along the planes of lines III-III and IV-IV, respectively, of FIGURE 2.

Referring now in detail to the drawings, my cell includes a tray of channel section, the bottom or floor of which serves as an anode plate. In the arrangement shown, two trays are disposed in alinement, back-to-back, and may form a unitary structure. A weir 11 is located at the end of each tray which is remote from the other. A collecting trough 12 extends below the weir 11 to receive electrolyte overflowing it.

A tank 13 contains a supply of electrolyte, e.g., acidic zinc sulphate. It is connected to trough 12 by a pipe 14 and is provided with an electrolyte regenerator 15 of known type containing metallic zinc. A pump 16 draws electrolyte from tank 13 and delivers it through a pipe connection 17 to an inlet chamber 18. Chamber 18 ex- 3,354,070 Patented Nov. 21, 1967 tends upwardly from below tray 10 and opens into the bottom thereof. Pipe 17 and chamber 18 are duplicated or twinned to serve the two trays 10 arranged end-to-end.

Chamber 18 has a bifurcated inlet pipe 19 with an opening sized for connection to pipe 17. The branched arms of pipe 19 extend to the entrances of chamber 18. From these entrances, the chamber flares laterally to an outlet 20 substantially the full width of tray 10. The inlet chamber 20 has an inlet means, such as inlets 19a having a cross sectional area substantially less than the cross sectional area of an electrolyte inlet 20a from the passageway 20 to the trays 10, an outlet 20b to the passageway 20 having a cross sectional area substantially the same as the electrolyte inlet 20a and a tapering body portion 18a connecting the inlets 19a to the inlet chamber 18 to the outlet 20b of the inlet chamber 20. By virtue of this construction, the velocity of electrolyte flow is reduced from the high value at which it traverses pipe 17, e.g., approximately 100 f.p.m., to a relatively low value of less than 25 f.p.m. at passageway 20. This avoids any fountain eflect, or excessive turbulence and splashing, and causes the electrolyte to flow smoothly and without turbulence from outlet 20b of chamber 18 through passageway 20 and electrolyte outlet 20b onto trays 10 on both sides thereof and thence along them both to weirs 11. A minimum of 5 g.p.m. of electrolyte flow per inch of tray width at a minimum flow rate of feet per minute must be maintained between the strip S and the tray 10 (anode) to provide satisfactory conductivity between the anode 10 and the strip S. By his practice a plating current density of 500 amps per sq. ft. may be achieved, which is required for successful commercial operation.

Pairs of pinch rolls 21 located above each trough 12 convey strip S along the trays 10 at a short distance above the bottom thereof. At least one roll 21 of each pair is conducting and is connected to the negative terminal of a current source such as generator 22. The other terminal of the source is connected to the tray 10.

As will be evident from the drawings, the relationship of the trays 10, weirs 11 and pinch rolls 21 is such that the flow of electrolyte over the weirs 11 may be maintained so the strip S will travel through the flowing electrolyte at a level just below its surface, say Ms" or A. This prevents any substantial plating of the upper surface of the strip S except at the extreme edges. The cell of my invention is thus particularly useful in making strip coated on one side only (one-side galvanized), for which there is a present commercial demand. The avoidance of throwaround is further aided by longitudinal vertical baflfles 24 depending from bridges 25 extending transversely of tray 10, close to the strip edges as shown in FIG- URE 4.

A further advantage of the invention is that the flowing electrolyte tends to scavenge gas bubbles from the surface of the strip S. The underlying advantage, of course, is that the desired volume of flow of electrolyte may be achieved without excessive turbulence anywhere in the stream.

Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention.

I claim:

1. Electroplating apparatus for plating a permanent coating of a metal on a moving strip serving as a cathode and having:

(a) a tray adapted to contain flowing electrolyte and to serve as an anode;

(b) a weir disposed at one end of said tray to determine the level of flowing electrolyte in said tray;

(c) means for transporting said moving strip through said flowing electrolyte and over said weir at a level .just below the surface of said flowing electrolyte to substantially eliminate plating of the upper surface of said moving strip;

(d) said tray having an electrolyte inlet spaced from said weir and extending substantially the full width of Said tray;

,(e) collecting means adjacent said Weir for collecting the overflow of electrolyte from said Weiif) an inlet chamber in communication with said electrolyte inlet and said collecting means tor reducing the velocity of electrolyte Jflow from said eolleoting means to said electrolyte inlet and for eliminating any fountain .efliect, excessive turbulence and Splashing as said electrolyte flows into said electrolyte inlet and toward said weir;

(8) said inlet chamber having an inlet means having across sectional .area substantially less than the cross sectional area .of said electrolyte inlet, an outlet havi a .cross sectional area substantially the same as said electrolyte inlet and a tapering body portion connecting said inlet means to Said outlet; and

, (h) circulating means connected to said collecting means and to said inlet chamber for circulating said electrolyte between said electrolyte inlet and said .weir.

7 2. The electroplating apparatus recited in claim 1 wherein .said collecting means is a collecting trough.

3. The electroplating apparatus recited in claim 2 wherein said collecting trough is in communication with a tank.

4. The electroplating apparatus recited in claim 3 and having an electrolyte regenerator in communication with said tank.

5. The electroplating apparatus recited in claim 1 and having a bafifle means mounted on .sa-id tray -and extending along the path of movement of said moving strip to avoid throw around of electrolyte onto the upper surface of said moving strip.

6. The electroplating means recited in claim 1 wherein said inlet means is a pair of opposed inlets disposed on each side of said outlet.

References Cited UNITED STATES PATENTS 1,438,722 2/ 1924 EustiS n.-- 204-237 X 2,445,675 7/1948 Lang v 204F209 2,490,055 12/ 1949 Hofi 204-1206 2,75 8,075 8/ 1956 .swalheirn 7-. 20428 2,924,563 2/ 1960 Gray 204198 J-O HN MACK. Primary Examiner.

VAN ,SISE, Assistant Examiner. 

1. ELECTROPLATING APPARATUS FOR PLATING A PERMANENT COATING OF A METAL ON A MOVING STRIP SERVING AS A CATHODE AND HAVING: (A) A TRAY ADAPTED TO CONTAIN FLOWING ELECTROLYTE AND TO SERVE AS AN ANODE; (B) A WEIR DISPOSED AT ONE END OF SAID TRAY TO DETERMINE THE LEVEL OF FLOWING ELECTROLYTE IN SAID TRAY; (C) MEANS FOR TRANSPORTING SAID MOVING STRIP THROUGH SAID FLOWING ELECTROLYTE AND OVER SAID WEIR AT A LEVEL JUST BELOW THE SURFACE OF SAID FLOWING ELECTROLYTE TO SUBSTANTIALLY ELIMINATE PLATING OF THE UPPER SURFACE OF SAID MOVING STRIP; (D) SAID TRAY HAVING AN ELECTROLYTE INLET SPACED FROM SAID WEIR AND EXTENDING SUBSTANTIALLY THE FULL WITH OF SAID TRAY; (E) COLLECT MEANS ADJACENT SAID WEIR FOR COLLECTING THE OVERFLOW OF ELECTROLYTE FROM SAID WEIR; (F) AN INLET CHAMBER IN COMMUNCATION WITH SAID ELECTROLYTE INLET AND SAID COLLECTING MEANS FOR REDUCING THE VELOCITY OF ELECTROLYTE FLOW FROM SAID COLLECTING MEANS TO SAID ELECTROLYTE INLET AND FOR ELIMINATING ANY FOUNTAIN EFFECT, EXCESSIVE TURBULENCE AND SPLASHING AS SAID ELECTROLYTE FLOWS INTO SAID ELECTROLYTE INLE AND TOWARD SAID WEIR; 